(Thanks to the alliance leader of "Greasy Night" for the reward, +2 for owing, thanks to the "SP55AA" 10,000 reward, +2 for the promotion of the alliance leader, and thanks for the reward of "Evening Clouds Collect a Light Sky".) Total underpayment 7)

When Cheng Mo returned to the classroom, it had been more than ten minutes since he was in class, this was the first time in his life that he was late, and his mood was extremely complicated, but the complexity was not entirely due to being late.

He stood at the back door of the classroom, his sticky shirt clinging to his skin, and his soaked hair was also on his forehead, making him uncomfortable, Cheng Mo hesitated for a moment, turned around and walked to the window of the stairwell, dragging the glass window, the fresh wind blew in, making him feel cold. Cheng Mo held the window lattice with both hands, looking at the road from the teacher's dormitory, he guessed that Teacher Shen should come to the teaching building soon, but no matter how much he waited, he couldn't find anything.

The sky is blue, the soft clouds are blown around by the wind, the branches and leaves of the bamboo forest not far away are swaying in the breeze, and the voice of the class reading English pierces the eardrums.

Cheng Mo knew where this feeling came from, irrational emotions and desires were the guinea pigs he was locked in a cage, and he was holding a rational knife and preparing to dissect it carefully, just waiting for the moment when Teacher Shen came. He looked at the path in the bamboo forest without moving, as if he was looking at his heart through a microscope, but the empty path was not visited for a long time.

Until the bell rang for the end of class, Cheng Mo didn't wait, turned around and walked down the stairs, and went straight to the first (9th) class of high school, when he arrived at the back door. Tang Wenjun, who had just walked out of the classroom and was about to go to the commissary to buy a drink, greeted Cheng Mo warmly when he saw him, "Brother Mo, why haven't you found anything yet?"

In the morning, when Cheng Mo and Fu Yuanzhuo came to the first (9th) class of high school together, the two of them came to find something under an excuse.

Cheng Mo nodded.

Tang Wenjun said enthusiastically: "What is it? Can you say it? I can also help find it." ”

"A sticky note with important notes. Cheng Mo casually said nonsense.

"Is it on the podium?"

"Hmm!"

"I'll help you find it. Tang Wenjun took the initiative to say.

Cheng Mo didn't refuse, and it was a little abrupt to ask him to rush to the lower grade classroom alone, so he followed Tang Wenjun into the classroom of the first (9th) class of high school, which was very lively, the freshmen of the first year of high school were playing, chatting, and playing with their mobile phones, and no one paid attention to him.

At this time, the mobile phone shook twice, Cheng Mo guessed that it was Fu Yuanzhuo, took out the mobile phone and looked at it, sure enough, he replied "Go to the classroom immediately", put the mobile phone back in his pocket, and looked up at the red letters above the blackboard and the roof.

As he expected, the plastic made of "good at learning and erudition, happy to read and think" is exceptionally bright, shining in the sun, he looked at the roof again, but he couldn't see anything abnormal, Cheng Mo reached out and touched the invisible powder in his pocket, and said directly to Tang Wenjun: "I'll go to the podium to look for it, you help me find ..... here on the podium."

"Okay! Brother Mo, is it a sticky note?"

"Yes, a white square of paper..... "Even if he tells a casual lie, Cheng Mo will be very particular about details.

"Good. ”

Tang Wenjun lowered his head and bent down to rummage in the podium, while Cheng Mo walked straight to the cabinet Gree air conditioner placed in the corner of the classroom, the style is very old and rectangular, the air outlet is obliquely facing the classroom, the LCD screen does not occupy a large area, and the white plastic shell is slightly yellowed.

Cheng Mo walked to the side of the air conditioner, squatted down and looked at the terrazzo floor behind the air conditioner, as he guessed, there were shallow abrasion marks on the gray and white ground, he turned his head to look at the blackboard, at this time, the sunlight shone directly on the left side of the blackboard from the outside of the window, and there was a large halo, if you don't close the curtains, you can't see the handwriting on the blackboard.

Cheng Mo probably had already reasoned out how the other party had completed this secret room, he stood up, returned to the podium, pretended to look for Tang Wenjun for a while, and when the class time was almost up, he looked at the table below, patted Tang Wenjun on the shoulder and said, "Forget Tang Wenjun, don't look for it....."

Tang Wenjun straightened up, "Otherwise, I'll wait for the class to start, and the classmates will help you look around the classroom." ”

Cheng Mo shook his head, "No need, it's not a big deal if you can't find it, it's just some data in our class, just recount it." ”

Tang Wenjun let out an "oh" and said, "That's sorry! Brother Mo, I didn't help much." ”

"I'm sorry to say I'm sorry, I'll invite you to dinner another day. ”

Tang Wenjun smiled, "Don't, Brother Mo, you have to invite you to dinner for this little thing, so it's polite....."

"Definitely. Cheng Mo waved his hand, didn't say more, and walked towards the outside of the classroom, as long as he verified one thing, he could decipher how the "Secret Room Painting" appeared instantly.

But at the moment, what he was thinking about was not this matter, but another thing, in fact, it was not the key to cracking the secret of the completion of the "Secret Room Painting", the key was how to find the person who painted it.

And to find this person, you must understand what is the motive and purpose of the other party's design of such a delicate and ingenious "joke"?

If it's just to tease Teacher Shen, it's too boring.

If the other party is because he has a crush on Mr. Shen, then what do those paintings mean?

If the other person is a student, then who else in this school can have such a deep understanding of art, such superb drawing skills, and a passion for reasoning?

The more Cheng Mo thought about it, the more strange he felt, the more he thought about it, the more incredible he felt, he took out his mobile phone, found Shen Mengjie's WeChat, and sent a message, "Shen Mengjie, does Teacher Shen still have a twin sister?"

Cheng Mo didn't put the phone back in his pocket, but walked up with the phone, and when he walked to the second floor, he received a reply from Shen Mengjie, "Yes..... But how do you know that?"

This answer made Cheng Mo a little surprised, it was completely different from what he guessed, he stood at the exit of the stairwell, looked at his phone and frowned, and then typed and asked, "So where is Teacher Shen's sister now?"

——————————————————

Cheng Mo returned to the classroom, feeling that his head was as big as a fight, he hadn't asked Shen Mengjie about Shen Daoyi, he just thought that this matter was very interesting, and it was a puzzle worth looking for the answer to for him, if he asked Shen Mengjie, it was tantamount to looking at the answer directly without solving the problem, so Cheng Mo didn't do it.

But after Shen Daoyi might be involved in the incident of "Painting of the Secret Room", he had to ask Shen Mengjie about Shen Daoyi's situation, so he got an answer that met his imagination, but it was still very bizarre.

When Cheng Mo walked into the classroom and sat back in his seat, the class bell happened to ring, and he didn't care that the math teacher was in class, so he took out his mobile phone and looked at the ten paintings again.

Yan Yitong, who was sitting in front, leaned his back against Cheng Mo's desk, and handed over a book that had been opened with his backhand and placed it on Cheng Mo's desk.

Cheng Mo put down his phone, and Yan Yitong's mellow and lovely handwriting was on the notebook: "Cheng Mo, is your body okay, are you?, why have you been checking it for so long?"

Cheng Mo saw Yan Yitong's cute comics, smiled slightly, picked up the pen and wrote: "It's okay, I'm in good physical condition..... After finishing writing, he rolled up the soft notebook with this pink cartoon cover, stabbed Yan Yitong's back, and then handed it to Yan Yitong's hand.

Yan Yitong took the notebook, leaned over and began to write again, and after a while, she put the notebook on Cheng Mo's desk.

Cheng Mo flipped through it, and under the answer he wrote, Yan Yitong drew another cheering and exploding villain, the cartoon villain raised his hands and jumped up, and drew a lot of lines representing light around his body, and there was a dialogue bubble next to it, which read, "Good Kaisen!

Cheng Mo had never paid attention to others in class, but he also wanted to take the opportunity to empty his somewhat chaotic thoughts, so he deserted during class time, returned a classic little yellow face and smiled expression, and re-stuffed it to Yan Yitong.

Yan Yitong quickly put the notebook back again, and there was a picture of an explosive-headed villain with a knife, fork and hammer, banging on another villain with glasses like thunder, "Wrong answer, negative score, please accept the crit from Yan Xiaoniu, and answer the correct answer: How to eat spicy strips? I want to invite you to a big meal....."

Cheng Mo wrote: "Then I'll treat you to a pack of spicy strips, this meal is big enough!"

.......

The two of them wrote boring conversations in their notebooks, until the math teacher found Yan Yitong looking at the notebook on the table in class, laughing like a nymphomaniac, so he held the podium with both hands, looked at Yan Yitong and said, "Yan Yitong, stand up and tell me how to do this problem....."

The math teacher turned around and wrote on the blackboard: "If the non-zero function f(x) is for any real number x, y has f(x)•f(y)=f(xy), and when x0 f(x)1.

(1) Verification: f(x)0;

(2) Verification: f(x) is the subtraction function on R;

(3) At that time, for a-1,1, the value range of the real number x is ......"

Yan Yitong bit her lip and stood up a little embarrassed, she hadn't recovered from the great joy of Cheng Mo and her passing notes in class, and the math problems on the blackboard were all symbols that she couldn't understand.

Just when Yan Yitong didn't know what to do, Cheng Mo had already whispered the answer behind her back: "f(0)•f(x)=f(x),

i.e. f(x)f(0)-1=0,

f(x)0,

f（0）=1

When x0, f(x)1,

then -x0,

f（x）•f（﹣x）=f（0）=1......”

The sun was shining on Yan Yitong's back, making her feel warm.....